Astronomy - Astrophotography

Astronomy is a large scientific area where new discoveries and new hypothesis about our universe
are made almost every week. In contrast to other natural sciences the dimensions in astronomy are of an extreme
large order so that distances have to be expressed in terms of astronomical units (1AU = 149.6 Mio Km)) within our
solar system and in the units of lightyears
(ly) and parsec for objects beyond (1ly = 9,460,730,472,580km and 1parsec = 3.262 ly = 30'856'802'500'000'000km).

Our own galaxy is a small patch in the universe, expanding about 100'000 ligthyears across. It consists of about
100 to 300 Billion stars and most objects we can observe in the sky lie within this area - between just a few and
many thousand lightyears away. Due to the large distances of even the closests stars the night sky seems to
be a fixed rotating system over the period of a human life and hardly any change can be detected. In reality though,
most stars, nebulas and other particles speed around with many kilometers per second. Our sun and the solar
system is no exception. It orbits the galacital center within about 211 Million years.Basically all galacical
nebulas, open and globular clusters that can be seen from earth are objects belonging to our galaxy. But that is
by far not the end! There are other 'star islands' within the otherwise almost empty space. One of the closest
galaxy is the Andromeda Galaxy that itself consists roughly of another 1000 billion
stars. Light emitted by those stars has to travel 2.5 million years before reaching the earth. Therefore we see the
galaxy as it looked like 2.5 million years ago. As an extrem example, the
Hubble space telescope captured light that was travelling for
more than 13 billion years. In fact, these photons have been on there way for such a long time that they show an
image of our universe shortly after it is believed to be formed.

If you ever have been high up the mountains or at another remote place far from any light polluted area, you
may have wondered how much more stars appear. Even though our eyes are not very sensitive in the dark, the
galactical plane (milkyway) reveals fantastic
structures including dark dust bands crossing the illuminated background of countless stars. If we want to see
individual objects we need the dim light to be concentrated before reaching our eyes. A telescope exactly does this
job. The amount of objects that can be seen even with a small telescope is remarkable but even with the largest
telescopes most objects in the sky appear just as gray objects - without color. That is not because the universe has
no color - not at all, but it is because even the concentrated light is not bright enough for our eyes to make the
color differentiation.

The barrier of grayscaled images can be negotiated by adding a (CCD-)camera. In each
fraction of a second our eyes produce an image out of what reaches the retina in that moment. In contrast to our
organ of sight, a camera whose shutter is open for a couple of minutes can integrate all the light particles that
reach the detector during this time interval, producing an image with a lot more details and faint structurs.
Therefore light that is extremely faint can only be detected with a CCD-camera and information can be extracted
to display the object in color. Once the light is captured it is another step to produce a good contrasted aesthetic
image. Click here to understand why image processing is a 'must' in astrophotography.